Cold Rheem

Working on a Rheem natural gas furnace. It's got the "jet" type burners. Four burners. 80 percenter.
The inducer blows, the HSI heats, the gas lights. And lights all the way across. About a second later, the gas shuts off. And, the whole thing goes through the routine again.
The call came in Friday about 6 PM. Didn't have a sensor rod, so Monday I bought one.
Now, even with a new sensor rod, and a new grounding screw, it's still the same. Fires for a second, and then shuts down.
The furnace is a 1999 model now. Has had essentially no maint except for filter changes.
I checked the ground to neutral at the furnace (less than one ohm) and the connection between the terminal and the molex connector where it comes off the main board. Also less than one ohm. Then checked the ground screw from the sensor rod to the 110 VAC ground. Again, nothing.
Guess the only grounding thing I didn't check was that the ground wire from the 110 VAC was connected to the case of the furnace. Is that relevant?
What else to check, or is it time to replace the board?
--

Christopher A. Young
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Stormin Mormon wrote:

Did you check the flame current? Why did you replace the sensor? Why are you working on a system that you don't understand?
hvacrmedic
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More importantly, whay aren't you asking the "professionals" over at alt.hvac ? Or as they would tell you there, hire a "professional" LOL.
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No, I didn't check the current from the flame sensor. Supposed to be 2 to 4 microamps.
I'm working on a system that I don't understand cause it belongs to a friend of mine. And, this is the kind of case where I learn all sorts of things about trouble shooting.
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Stormin Mormon wrote:

What have you learned so far? And BTW who's paying for the new sensor that it didn't need? What happens if you put a new board on it and it still doesn't work? Do you know how to trouble shoot the board? Are you willing to put your own money up on nothing other than possibility that the board is at fault?
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Hey FDR, he hangs out at alt.hvac. We think he's a hack. This proves it.

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On Tue, 25 Oct 2005 15:46:13 GMT, "Stormin Mormon"

It's time to call someone who knows what they are doing. +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ spam protection measure, Please remove the 33 to send e-mail
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"someone" is singular, and "they" is plural. Can't use them in conjunction like that. It isn't how them words are used.
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Christopher A. Young
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Stormin Mormon wrote:

alt.hvac, not here. <grin>
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Oh, I'm so terribly sorry. Want me to donate to your cat shelter? (big grin)
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Christopher A. Young
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Black and orange stray cat sittin' on a fence Ain't got enough dough to pay the rent I'm flat broke but I don't care I strut right by with my tail in the air
Stray cat strut, I'm a ladies' cat, A feline Casanova, hey man, thats where its at Get a shoe thrown at me from a mean old man Get my dinner from a garbage can
Yeah don't cross my path
I don't bother chasing mice around I slink down the alley looking for a fight Howling to the moonlight on a hot summer night Singin' the blues while the lady cats cry, "Wild stray cat, you're a real gone guy."
I wish I could be as carefree and wild, but I got cat class and I got cat style.
I don't bother chasing mice around I slink down the alley looking for a fight Howling to the moonlight on a hot summer night Singin' the blues while the lady cats cry, "Wild stray cat, you're a real gone guy."
I wish I could be as carefree and wild, but I got cat class and I got cat style.
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That's really great. Scuse me while I cross post to a kitty board.
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Christopher A. Young
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Flame sense current, or continue to throw parts at it until something sticks! Greg
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I'm running out of parts to throw. Seeing as how I replaced the flame sensor already.
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Well Stormy, without knowing for sure what the flame sense microamps are it could be anyone's guess. it may not be either the board or the flame rod, maybe you have a bad gas valve that just drops off for no good reason. We had a new Ruud RTU that would drop the gas valve for no reason, ended up being a bad burner for no obvious reason. Greg
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This is Turtle.
I got into this years back on the 1988 to 2000 Rheem gas furnaces and depending on the model you have , I saw 4 of them do the samething and end up calling Rheem tech support for nothing would stick to regular trouble shooting thinking and they ended up call all 4 as then and but 3 later. They said change the flame sencer and if it did not work . Change the relay board. Rheem tech support would not say why this was the cure.
TURTLE
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Yes, that's about where I am, in the troubleshooting process.
One other person suggested to pull the burners, and give them a good cleaning out. In case the fire isn't hot enough (on the very farthest burner away from the gas valve). Might not be hot enough to be sensed.
However, it's looking more and more like time to change the board. Maybe a new board will work better. I've got an OEM board from one parts house, and then J'stone has an aftermarket board which is about 1/3 cheaper. Do you only do OEM boards? I figure in this case, the aftermarket board might last a while. This particular HO has next to no money.
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This is Turtle.
Stormy , I would be careful putting after market board on the Rheem 1988 to 2000 model gas furnaces. other years i would say different.
TURTLE
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